perlintern - autogenerated documentation of purely inter-
nal Perl functions
This file is the autogenerated documentation of functions
in the Perl interpreter that are documented using Perl's
internal documentation format but are not marked as part
of the Perl API. In other words, they are not for use in
extensions!
CV reference counts and CvOUTSIDE [Toc] [Back] CvWEAKOUTSIDE
Each CV has a pointer, "CvOUTSIDE()", to its lexically
enclosing CV (if any). Because pointers to
anonymous sub prototypes are stored in "&" pad
slots, it is a possible to get a circular reference,
with the parent pointing to the child and
vice-versa. To avoid the ensuing memory leak, we
do not increment the reference count of the CV
pointed to by "CvOUTSIDE" in the one specific
instance that the parent has a "&" pad slot pointing
back to us. In this case, we set the "CvWEAKOUTSIDE"
flag in the child. This allows us to
determine under what circumstances we should
decrement the refcount of the parent when freeing
the child.
There is a further complication with non-closure
anonymous subs (ie those that do not refer to any
lexicals outside that sub). In this case, the
anonymous prototype is shared rather than being
cloned. This has the consequence that the parent
may be freed while there are still active children,
eg
BEGIN { $a = sub { eval '$x' } }
In this case, the BEGIN is freed immediately after
execution since there are no active references to
it: the anon sub prototype has "CvWEAKOUTSIDE" set
since it's not a closure, and $a points to the
same CV, so it doesn't contribute to BEGIN's refcount
either. When $a is executed, the "eval
'$x'" causes the chain of "CvOUTSIDE"s to be followed,
and the freed BEGIN is accessed.
To avoid this, whenever a CV and its associated
pad is freed, any "&" entries in the pad are
explicitly removed from the pad, and if the refcount
of the pointed-to anon sub is still positive,
then that child's "CvOUTSIDE" is set to
point to its grandparent. This will only occur in
the single specific case of a non-closure anon
prototype having one or more active references
(such as $a above).
One other thing to consider is that a CV may be
merely undefined rather than freed, eg "undef
&foo". In this case, its refcount may not have
reached zero, but we still delete its pad and its
"CvROOT" etc. Since various children may still
have their "CvOUTSIDE" pointing at this undefined
CV, we keep its own "CvOUTSIDE" for the time
being, so that the chain of lexical scopes is
unbroken. For example, the following should print
123:
my $x = 123;
sub tmp { sub { eval '$x' } }
my $a = tmp();
undef &tmp;
print $a->();
bool CvWEAKOUTSIDE(CV *cv)
Functions in file pad.h [Toc] [Back] CX_CURPAD_SAVE
Save the current pad in the given context block
structure.
void CX_CURPAD_SAVE(struct context)
CX_CURPAD_SV
Access the SV at offset po in the saved current
pad in the given context block structure (can be
used as an lvalue).
SV * CX_CURPAD_SV(struct context, PADOFFSET po)
PAD_BASE_SV
Get the value from slot "po" in the base (DEPTH=1)
pad of a padlist
SV * PAD_BASE_SV (PADLIST padlist,
PADOFFSET po)
PAD_CLONE_VARS
|CLONE_PARAMS* param Clone the state variables
associated with running and compiling pads.
void PAD_CLONE_VARS(PerlInterpreter
*proto_perl
PAD_COMPNAME_FLAGS
Return the flags for the current compiling pad
name at offset "po". Assumes a valid slot entry.
U32 PAD_COMPNAME_FLAGS(PADOFFSET po)
PAD_COMPNAME_GEN
The generation number of the name at offset "po"
in the current compiling pad (lvalue). Note that
"SvCUR" is hijacked for this purpose.
STRLEN PAD_COMPNAME_GEN(PADOFFSET po)
PAD_COMPNAME_OURSTASH
Return the stash associated with an "our" variable.
Assumes the slot entry is a valid "our"
lexical.
HV * PAD_COMPNAME_OURSTASH(PADOFFSET
po)
PAD_COMPNAME_PV
Return the name of the current compiling pad name
at offset "po". Assumes a valid slot entry.
char * PAD_COMPNAME_PV(PADOFFSET po)
PAD_COMPNAME_TYPE
Return the type (stash) of the current compiling
pad name at offset "po". Must be a valid name.
Returns null if not typed.
HV * PAD_COMPNAME_TYPE(PADOFFSET po)
PAD_DUP Clone a padlist.
void PAD_DUP(PADLIST dstpad, PADLIST
srcpad, CLONE_PARAMS* param)
PAD_RESTORE_LOCAL
Restore the old pad saved into the local variable
opad by PAD_SAVE_LOCAL()
void PAD_RESTORE_LOCAL(PAD *opad)
PAD_SAVE_LOCAL
Save the current pad to the local variable opad,
then make the current pad equal to npad
void PAD_SAVE_LOCAL(PAD *opad, PAD
*npad)
PAD_SAVE_SETNULLPAD
Save the current pad then set it to null.
void PAD_SAVE_SETNULLPAD()
PAD_SETSV
Set the slot at offset "po" in the current pad to
"sv"
SV * PAD_SETSV (PADOFFSET po, SV*
sv)
PAD_SET_CUR
Set the current pad to be pad "n" in the padlist,
saving the previous current pad.
void PAD_SET_CUR (PADLIST padlist,
I32 n)
PAD_SET_CUR_NOSAVE
like PAD_SET_CUR, but without the save
void PAD_SET_CUR_NOSAVE (PADLIST
padlist, I32 n)
PAD_SV Get the value at offset "po" in the current pad
void PAD_SV (PADOFFSET po)
PAD_SVl Lightweight and lvalue version of "PAD_SV". Get
or set the value at offset "po" in the current
pad. Unlike "PAD_SV", does not print diagnostics
with -DX. For internal use only.
SV * PAD_SVl (PADOFFSET po)
SAVECLEARSV
Clear the pointed to pad value on scope exit. (ie
the runtime action of 'my')
void SAVECLEARSV (SV **svp)
SAVECOMPPAD
save PL_comppad and PL_curpad
void SAVECOMPPAD()
SAVEPADSV
Save a pad slot (used to restore after an iteration)
XXX DAPM it would make more sense to make the arg
a PADOFFSET void SAVEPADSV (PADOFFSET po)
Functions in file pp_ctl.c [Toc] [Back] find_runcv
Locate the CV corresponding to the currently executing
sub or eval. If db_seqp is non_null, skip
CVs that are in the DB package and populate
*db_seqp with the cop sequence number at the point
that the DB:: code was entered. (allows debuggers
to eval in the scope of the breakpoint rather than
in in the scope of the debugger itself).
CV* find_runcv(U32 *db_seqp)
PL_DBsingle
When Perl is run in debugging mode, with the -d
switch, this SV is a boolean which indicates
whether subs are being single-stepped. Singlestepping
is automatically turned on after every
step. This is the C variable which corresponds to
Perl's $DB::single variable. See "PL_DBsub".
SV * PL_DBsingle
PL_DBsub
When Perl is run in debugging mode, with the -d
switch, this GV contains the SV which holds the
name of the sub being debugged. This is the C
variable which corresponds to Perl's $DB::sub
variable. See "PL_DBsingle".
GV * PL_DBsub
PL_DBtrace
Trace variable used when Perl is run in debugging
mode, with the -d switch. This is the C variable
which corresponds to Perl's $DB::trace variable.
See "PL_DBsingle".
SV * PL_DBtrace
PL_dowarn
The C variable which corresponds to Perl's $^W
warning variable.
bool PL_dowarn
PL_last_in_gv
The GV which was last used for a filehandle input
operation. ("<FH>")
GV* PL_last_in_gv
PL_ofs_sv
The output field separator - $, in Perl space.
SV* PL_ofs_sv
PL_rs The input record separator - $/ in Perl space.
SV* PL_rs
is_gv_magical
Returns "TRUE" if given the name of a magical GV.
Currently only useful internally when determining
if a GV should be created even in rvalue contexts.
"flags" is not used at present but available for
future extension to allow selecting particular
classes of magical variable.
bool is_gv_magical(char *name, STRLEN
len, U32 flags)
start_glob
Function called by "do_readline" to spawn a glob
(or do the glob inside perl on VMS). This code
used to be inline, but now perl uses "File::Glob"
this glob starter is only used by miniperl during
the build process. Moving it away shrinks
pp_hot.c; shrinking pp_hot.c helps speed perl up.
PerlIO* start_glob(SV* pattern, IO *io)
CvPADLIST
CV's can have CvPADLIST(cv) set to point to an AV.
For these purposes "forms" are a kind-of CV,
eval""s are too (except they're not callable at
will and are always thrown away after the eval""
is done executing).
XSUBs don't have CvPADLIST set - dXSTARG fetches
values from PL_curpad, but that is really the
callers pad (a slot of which is allocated by every
entersub).
The CvPADLIST AV has does not have AvREAL set, so
REFCNT of component items is managed "manual"
(mostly in pad.c) rather than normal av.c rules.
The items in the AV are not SVs as for a normal
AV, but other AVs:
0'th Entry of the CvPADLIST is an AV which represents
the "names" or rather the "static type
information" for lexicals.
The CvDEPTH'th entry of CvPADLIST AV is an AV
which is the stack frame at that depth of recursion
into the CV. The 0'th slot of a frame AV is
an AV which is @_. other entries are storage for
variables and op targets.
During compilation: "PL_comppad_name" is set to
the names AV. "PL_comppad" is set to the frame AV
for the frame CvDEPTH == 1. "PL_curpad" is set to
the body of the frame AV (i.e. AvARRAY(PL_comppad)).
During execution, "PL_comppad" and "PL_curpad"
refer to the live frame of the currently executing
sub.
Iterating over the names AV iterates over all possible
pad items. Pad slots that are SVs_PADTMP
(targets/GVs/constants) end up having &PL_sv_undef
"names" (see pad_alloc()).
Only my/our variable (SVs_PADMY/SVs_PADOUR) slots
get valid names. The rest are op targets/GVs/constants
which are statically allocated or resolved
at compile time. These don't have names by which
they can be looked up from Perl code at run time
through eval"" like my/our variables can be.
Since they can't be looked up by "name" but only
by their index allocated at compile time (which is
usually in PL_op->op_targ), wasting a name SV for
them doesn't make sense.
The SVs in the names AV have their PV being the
name of the variable. NV+1..IV inclusive is a
range of cop_seq numbers for which the name is
valid. For typed lexicals name SV is SVt_PVMG and
SvSTASH points at the type. For "our" lexicals,
the type is SVt_PVGV, and GvSTASH points at the
stash of the associated global (so that duplicate
"our" delarations in the same package can be
detected). SvCUR is sometimes hijacked to store
the generation number during compilation.
If SvFAKE is set on the name SV then slot in the
frame AVs are a REFCNT'ed references to a lexical
from "outside". In this case, the name SV does not
have a cop_seq range, since it is in scope
throughout.
If the 'name' is '&' the corresponding entry in
frame AV is a CV representing a possible closure.
(SvFAKE and name of '&' is not a meaningful combination
currently but could become so if "my sub
foo {}" is implemented.)
AV * CvPADLIST(CV *cv)
cv_clone
Clone a CV: make a new CV which points to the same
code etc, but which has a newly-created pad built
by copying the prototype pad and capturing any
outer lexicals.
CV* cv_clone(CV* proto)
cv_dump dump the contents of a CV
void cv_dump(CV *cv, char *title)
do_dump_pad
Dump the contents of a padlist
void do_dump_pad(I32 level, PerlIO
*file, PADLIST *padlist, int full)
intro_my
"Introduce" my variables to visible status.
U32 intro_my()
pad_add_anon
Add an anon code entry to the current compiling
pad
PADOFFSET pad_add_anon(SV* sv, OPCODE op_type)
pad_add_name
Create a new name in the current pad at the specified
offset. If "typestash" is valid, the name is
for a typed lexical; set the name's stash to that
value. If "ourstash" is valid, it's an our lexical,
set the name's GvSTASH to that value
Also, if the name is @.. or %.., create a new
array or hash for that slot
If fake, it means we're cloning an existing entry
PADOFFSET pad_add_name(char *name,
HV* typestash, HV* ourstash, bool clone)
pad_alloc
Allocate a new my or tmp pad entry. For a my, simply
push a null SV onto the end of PL_comppad, but
for a tmp, scan the pad from PL_padix upwards for
a slot which has no name and and no active value.
PADOFFSET pad_alloc(I32 optype, U32
tmptype)
pad_block_start
Update the pad compilation state variables on
entry to a new block
void pad_block_start(int full)
pad_check_dup
Check for duplicate declarations: report any of:
* a my in the current scope with the same
name;
* an our (anywhere in the pad) with the same
name and the same stash
as "ourstash" "is_our" indicates that the
name to check is an 'our' declaration
void pad_check_dup(char* name, bool
is_our, HV* ourstash)
pad_findlex
Find a named lexical anywhere in a chain of nested
pads. Add fake entries in the inner pads if it's
found in an outer one. innercv is the CV *inside*
the chain of outer CVs to be searched. If newoff
is non-null, this is a run-time cloning: don't add
fake entries, just find the lexical and add a ref
to it at newoff in the current pad.
PADOFFSET pad_findlex(char* name,
PADOFFSET newoff, CV* innercv)
pad_findmy
Given a lexical name, try to find its offset,
first in the current pad, or failing that, in the
pads of any lexically enclosing subs (including
the complications introduced by eval). If the name
is found in an outer pad, then a fake entry is
added to the current pad. Returns the offset in
the current pad, or NOT_IN_PAD on failure.
PADOFFSET pad_findmy(char* name)
pad_fixup_inner_anons
For any anon CVs in the pad, change CvOUTSIDE of
that CV from old_cv to new_cv if necessary. Needed
when a newly-compiled CV has to be moved to a preexisting
CV struct.
void pad_fixup_inner_anons(PADLIST
*padlist, CV *old_cv, CV *new_cv)
pad_free
Free the SV at offet po in the current pad.
void pad_free(PADOFFSET po)
pad_leavemy
Cleanup at end of scope during compilation: set
the max seq number for lexicals in this scope and
warn of any lexicals that never got introduced.
void pad_leavemy()
pad_new Create a new compiling padlist, saving and updating
the various global vars at the same time as
creating the pad itself. The following flags can
be OR'ed together:
padnew_CLONE this pad is for a cloned
CV
padnew_SAVE save old globals
padnew_SAVESUB also save extra stuff for
start of sub
PADLIST* pad_new(int flags)
pad_push
Push a new pad frame onto the padlist, unless
there's already a pad at this depth, in which case
don't bother creating a new one. If has_args is
true, give the new pad an @_ in slot zero.
void pad_push(PADLIST *padlist, int
depth, int has_args)
pad_reset
Mark all the current temporaries for reuse
void pad_reset()
pad_setsv
Set the entry at offset po in the current pad to
sv. Use the macro PAD_SETSV() rather than calling
this function directly.
void pad_setsv(PADOFFSET po, SV* sv)
pad_swipe
Abandon the tmp in the current pad at offset po
and replace with a new one.
void pad_swipe(PADOFFSET po, bool refadjust)
pad_tidy
Tidy up a pad after we've finished compiling it:
* remove most stuff from the pads of anonsub
prototypes;
* give it a @_;
* mark tmps as such.
void pad_tidy(padtidy_type type)
pad_undef
Free the padlist associated with a CV. If parts
of it happen to be current, we null the relevant
PL_*pad* global vars so that we don't have any
dangling references left. We also repoint the
CvOUTSIDE of any about-to-be-orphaned inner subs
to the outer of this cv.
(This function should really be called pad_free,
but the name was already taken)
void pad_undef(CV* cv)
Stack Manipulation Macros [Toc] [Back] djSP Declare Just "SP". This is actually identical to
"dSP", and declares a local copy of perl's stack
pointer, available via the "SP" macro. See "SP".
(Available for backward source code compatibility
with the old (Perl 5.005) thread model.)
djSP;
LVRET True if this op will be the return value of an
lvalue subroutine
SV Manipulation Functions [Toc] [Back] report_uninit
Print appropriate "Use of uninitialized variable"
warning
void report_uninit()
sv_add_arena
Given a chunk of memory, link it to the head of
the list of arenas, and split it into a list of
free SVs.
void sv_add_arena(char* ptr, U32 size,
U32 flags)
sv_clean_all
Decrement the refcnt of each remaining SV, possibly
triggering a cleanup. This function may have
to be called multiple times to free SVs which are
in complex self-referential hierarchies.
I32 sv_clean_all()
sv_clean_objs
Attempt to destroy all objects not yet freed
void sv_clean_objs()
sv_free_arenas
Deallocate the memory used by all arenas. Note
that all the individual SV heads and bodies within
the arenas must already have been freed.
void sv_free_arenas()
The autodocumentation system was originally added to the
Perl core by Benjamin Stuhl. Documentation is by whoever
was kind enough to document their functions.
perlguts(1), perlapi(1)
perl v5.8.5 2002-11-06 11 [ Back ] |
